Populate more e-mail headers when sending activation e-mail
Support suppressing sending an activation e-mail

An API key is registered and self-assigned at the time that the parser
is first run. There's no sense in confirming the e-mail address, so for
that reason we provide the ability to suppress sending it out. Per #180.
Add some comments
Pivot the error-handling order of operations for database errors
Make the key name the same as the API key

This makes it faster to check whether a key exists than having to
iterate over the whole object.